1. Field of the Invention
This invention concerns an air-jet loom including a main jet nozzle for inserting the weft yarns into the loom shed and auxiliary, weftwise spaced nozzles mounted serially in the direction of motion of the weft yarns, the latter mounted on a batten and consisting of straight tubules closed at their free ends and tapered to a sharp tip near their ends. The auxiliary nozzles each furthermore are provided with an essentially plane lateral surface including at least one blow aperture directed upwardly towards an essentially U-shaped weft guide channel formed by reed blades of the loom and angled towards the direction of motion of the weft yarns.
2. Description of Related Information
A problem exists in air jet looms of the type mentioned above in regard to filling the reed-formed guide channel as uniformly as possible with the weft conveying air to assure reliable and problem-free weft conveyance. On the other hand, the air consumption for such conveyance must be minimized to keep the energy consumption of the jet loom as low as possible. Moreover, it has been found in practice that different weaving materials require strongly different air flows. Illustratively, it is easier to move a course cotton yarn with a moderate air flow than a filament yarn which demands a more intense air flow. Accordingly, practice usually demands that the auxiliary nozzle be operated at varying supply pressures.
It is known from German Auslegeschrift No. 21 19 238 to provide the auxiliary nozzles with blow apertures in the form of circular holes. It was found, however, that the direction of blowing for larger diameters of such nozzles varied with the applied auxiliary air pressure and shifted as this pressure varies. Therefore, such nozzles are appropriate only when the same material is being woven and when no change in air pressure is required.
It is further known from the German Patent No. 25 22 335 to provide a number of individual holes in an auxiliary nozzle arranged like a sieve in lieu of a single large aperture acting as the blow hole in the nozzles. These individual holes are arranged on a circular surface and are meant to divide the air into a number of separate jet streams which, a very short distance beyond the blow aperture, combine again into a single steam. It was found possible upon properly selecting the dimensions of the individual holes and upon suitably arraying them to improve the stability of the blow system, that essentially the same blow direction is retained even when the auxiliary air supply pressure varies. However, these individual holes cause flow losses which are cumulative and result in a higher total loss than a single large hole per auxiliary nozle. Moreover, it is a fairly complex and expensive procedure to produce the plurality of individual holes, and the small holes clog more easily, requiring laborious cleaning, for example by ultrasonic systems.
It is further known to provide auxiliary nozzles each having a blow aperture in the shape of a five-arm star. With this design, the blown-out air jet stream is divided at the exit from the blow aperture thereby presenting a substantially enlarged peripheral area in contact with the surrounding air. Accordingly, the blown out jet entrains comparatively much surrounding air as "secondary air", and a relatively small blown out air flow can generate a comparatively large flow of weft conveyance air. Compared to the design of the singular circular hole acting as the blow aperture, the stability of the star blow hole is somewhat improved at varying conveyance pressures. In this design, however, the directional stability does not assume a significant role, at least to the extent that the entrainment of secondary airproduces a relatively large air flow which in any event ultimately arrives in the channel formed by the reeds.